POWER AMPLIFIERS

The power amplifiers are large signal amplifiers which raise the power level of signals. The power amplifier may also be defined as a device which converts dc power to ac power and whose action is controlled by the input signal. In fact, the power amplifier draws power from dc power supply connected to the output circuit and converts it into useful ac signal power.

Difference between Voltage and Power Amplifiers

The primary function of the voltage amplifier is to raise the voltage level of the signal. It is designed to achieve the largest possible gain. Only very little power can be drawn from its output.

The voltage gain of an amplifier is given by the expression AV = ß Rc/Rin. So in order to achieve high voltage amplification

(i) transistors having thin base i.e. the transistors with high ß (exceeding 100) are used

(ii) input resistance RIN is kept quite low in comparison to RC and

(iii) to permit high collector load, which is necessary to give high voltage gain, the voltage amplifiers are always operated at low collector current (of the order of 1mA).

A power amplifier is required to deliver a large amount of power and such it has to handle large currents. So in order to achieve high power amplification (i) large sized power transistors are used in order to dissipate the heat produced in transistor during operation, (ii) transistors having thick base (i.e. transistors with comparatively smaller ß ) are used in order to handle large currents (iii) transformer coupling is used for impedance matching and (iv) collector resistance is made low.

Terms Used in Power Amplification

1. Collector efficiency is defined as the ratio of ac output signals to the zero signal power (or dc power supplied by the battery of a power amplifier). Power amplifiers are designed to give maximum collector efficiency.

2. Power dissipation capacity is defined as the ability of a power transistor to dissipate the heat developed in it.

3. Distortion is defined as the change of output wave-shape from the input wave shape of the amplifier. Distortion is produced because transistor is a non-linear device. Distortion is not a problem for small signals (i.e. voltage amplifiers) as transistor is a linear device for small variations about the operating point. However, a power amplifier handles large signals and, therefore, the problem of distortion arises.

Email Based Homework Assignment Help in Power Amplifiers

Transtutors is the best place to get answers to all your doubts regarding power amplifiers with examples. You can submit your school, college or university level homework or assignment to us and we will make sure that you get the answers you need which are timely and also cost effective. Our tutors are available round the clock to help you out in any way with electrical engineering.

Live Online Tutor Help for Methods for Power Amplifiers

Transtutors has a vast panel of experienced electrical engineering tutors who specialize in power amplifiers and can explain the different concepts to you effectively. You can also interact directly with our electrical engineering tutors for a one to one session and get answers to all your problems in your school, college or university level Electricalengineering. Our tutors will make sure that you achieve the highest grades for your electrical engineering assignments. We will make sure that you get the best help possible for exams such as the AP, AS, A level, GCSE, IGCSE, IB, Round Square etc.